I think most of the third-party votes are in the deep blue or red states where it wouldn't make any difference if they voted for Trump or Clinton instead.
My state usually has a higher proportion of third party votes than the US, nationally. That's because it's deep red, and voters feel they can safely cast a "protest" vote.
I don't think rational voters will do so in a battleground state.
After this election, I'm going to look at the close states and see if third-party voters could have changed the result. I don't expect to find any.
The 6% claiming that they support Gary Johnson (which I personally don’t buy) .......Very astute of you. The last five polls I’ve answered, I said I was voting for Johnson. In reality, I said “Who?”.